1. Field of the Invention
The present invention relates to the separation of impurities from polyols such as propoxylated glycerin by a procedure whereby the water content of the polyols is reduced by evaporation, to a modest level, and subsequently the resulting mixture is flashed to reduce the water content to 1000 ppm or lower and light organic impurities are thereafter stripped from the polyol.
2. Description of the Prior Art
Fatty acid--esterified propoxylated glycerins have been proposed for use as reduced caloric fat substitutes in food products. See, for example, U.S. Pat. No. 4,861,613.
These materials are conveniently prepared by esterification of propoxylated glycerin as described, for example, in U.S. Pat. Nos. 5,681,939 and 4,983,329.
The polyol which is employed in such esterification reactions should be free of contaminants which would adversely affect the ultimate use of the esterified propoxylated polyol, such impurities including allylic materials such allyl alcohol and other allylic compounds such as allyl alcohol ethers which are lower boiling that the polyol.
The present invention provides a process for the efficient separation of low boiling allylic impurities from propoxylated glycerin polyol.
Propoxylated glycerin polyol, as generally produced, contains substantial amounts of water and low boiling allylic impurities. Problems are encountered when attempts are made to strip low-boiling allylic materials from polyols which contain substantial amount of water.